Field of the Invention
The present invention relates generally to a tracking receiver which uses optical processing for detecting and tracking broadband chirp type emissions of unknown slope and bandwidth characteristics.
More particularly, the subject invention pertains to a tracking receiver as described which generates magnitude and directional information on the chirp emission for feedback controls from spatial frequency coordinates.
The present invention allows a broadband chirp type emission of unknown frequency slope and bandwidth characteristics to be detected and tracked. A chirp is a form of spread spectrum signal which generally exhibits very low spectral power density and, therefore, without the aid of a matched filter, it is extremely difficult to detect and track. This detection-tracking problem is compounded and made even more difficult when the chirp is of extremely broad bandwidth.
Based upon experience with airborne chirp radars, it has been observed that the detection process can be seriously hampered by high level interference, even for a comparatively narrow bandwidth chirp signal. This is due to the low spectral power density of a chirp signal. With a broad bandwidth chirp-like emission, the detection process is further complicated, particularly since the spectral power density generally decreases with increasing signal bandwidth.